Over the course of less than a century, the city has dropped more than 39 feet. MEXICO CITY (AP) — Mexico City is sinking by nearly 10 inches (about 25 centimeters) a year, according to new satellite imagery released this week by NASA, making it one of the world’s fastest-subsiding metropolises. One of the world’s most sprawling and populated urban areas, at 3,000 square miles (about 7,800 square kilometers) and some 22 million people, the Mexican capital and surrounding cities were built atop